1. Field of the Invention
The present invention relates to a brake cable system in which a bicycle brake cable is split from a single force application lug to a plurality of force transmission locations to apply brakes to the wheel of a bicycle. The bicycle brake cable system has particular applicability to the segment of the bicycle industry known as the freestyle market.
2. Description of the Prior Art
A conventional bicycle employs a frame upon which the seat, rear wheel, pedals, and drive transmission mechanism are mounted, and a steering assembly rotatably mounted relative to the frame. The major components of a bicycle steering assembly include a front wheel, a front wheel fork, a steering tube, a handlebar stem, and a set of handlebars. The steering assembly can be turned at an angle relative to the frame about an axis of rotation extending along the center of the steering tube of the steering assembly and the center of the head tube of the frame. The steering tube is mounting coaxially within the head tube of the bicycle frame and turns relative thereto on steering bearings interposed therebetween.
A number of years ago a rotatable brake cable coupling system was devised for use on a bicycle which allowed a rider to completely rotate the steering assembly of a bicycle as a unit relative to the bicycle frame on a bicycle having hand brakes. Prior to this time such a manipulation was not possible since the bicycle brake cables extending from the hand brake controls on the handlebars to the brake calipers of the brakes on the front and rear wheels of a bicycle would permit only limited rotation of the steering assembly relative to the frame to an arc of far less than 360 degrees.
However, a rotatable brake cable coupling system allows the front wheel, front wheel fork, steering tube, and handlebars of a bicycle to be rotated together through repeated 360-degree revolutions relative to the bicycle head tube by means of which the steering assembly is mounted to the bicycle frame. This feature allows riders to perform stunts while only the rear wheel of the bicycle is in contact with the riding surface. A bicycle having this capability is known in the industry as a "freestyle" bicycle.
One embodiment of a rotatable brake cable coupling system is described in Patent No. 084,322 issued in the Republic of China (Taiwan). Another rotatable brake cable coupling system is described in U.S. Pat. No. 5,791,671. Both of these systems are sold commercially as the Gyro rotatable brake coupling system by Bear Corporation located at 17101 So. Central Avenue, No. G, Carson, Calif. 90746.
Freestyle bicycle components are designed to be very stiff and strong, and are usually quite heavy as well. This type of construction ensures that they will withstand abuse from impact against cement, steel railings, and very high wooden ramps. Freestyle riders require all of the components of their bicycles, especially the braking system, to be not only reliable, but very responsive. The brake cable systems of freestyle bicycles must be free from inordinate flexing, since this leads to a loss of responsiveness in a braking system.
There are various subdivisions to the freestyle bicycle market. In flatland freestyle, bicycle tricks are performed on flat ground. The riders engage in spinning, balancing, and maneuvering their bicycle and body in innumerable orientations and at varying speeds. The riders try to go from one trick to another without ever touching any part of their body to the ground throughout their entire routines. "Pro-street" freestyling is typically done on a series of ramps that are arranged in several positions on a flat area of concrete. The ramps range from three to ten feet in height and can be adjacent, opposing, or at right angles to each other. On the average, "pro-street" riders do about eighty percent of their tricks in the air. These tricks include 360.degree. turns and flips. Other tricks are performed on steel bars and on the tops of ramps.
"Pro-vert" freestyling is done only on one ramp called a half pipe, which usually has a U-shaped configuration and is about twelve feet wide and eight to ten feet high. The half pipe is normally of a wooden construction. Pro-vert riders perform about ninety percent of their tricks in the air and while balancing on the edge or top of the half pipe. They soar into the air up to ten feet above the top of the ramp where they spin the steel bars, remove their feet from the pedals, or both. At the conclusion of such a trick they reposition their limbs and reenter the ramp to roll up the opposing side to perform another trick.
The form of freestyle riding known as dirt jumping is a mixture of BMX and freestyle riding. Riders perform stunts on a series of dirt jumps. They perform sets of triple jumps at four feet, five feet, and eight feet in height. Dirt jumping riders perform tricks similar to those of pro-street riders, but their landing must be more precise. The series of dirt jumps have steeper transitions than the ramps that pro-street and pro-vert rider use. Dirt jumping riders perform 360.degree. turns in the air, bar spinning, and back flip-type of tricks.
All of these freestyle riding systems require the use of a cable detangler, such as the Gyro rotatable brake coupling system. The proper function and responsiveness of such a cable detangler system is extremely important for the performance of tricks because the rider's safety is at stake.
In applying the bicycle brakes during freestyle tricks, riders must be able to both delicately feather (lightly drag) the brake pads and also fully engage the brake pads, thereby locking up their front or rear wheels from any rotation. This is done while balancing on either the front or rear wheel while on top of a ten-foot ramp or on a flat concrete surface. Freestyle riders must be able to rotate the handlebars or frame in the air without drag or flopping of the rotatable brake coupling system rotor. When dragging or flopping occurs, it is difficult for the rider to predict when and where to reach for the grips or pedals before landing. The reason for this difficulty is that the handlebars may be rotating. If there is a significant amount of dragging or flopping, the rate of rotation of the handlebars will be affected.
There are several factors involved in the lock up of the wheel and the smooth rotation of the handlebars relative to the bicycle frame. One of the most important factors is the cabling system, since this is the direct link from the rider to the brakes. Other variables include brake pad compression and friction coefficients, brake arm deflection, brake lever deflection, and frame and boss stiffness. While most of these other variables have been improved adequately by bicycle manufacturers in recent years, flexing and routing problems of the brake cable system have continued to exist. While attempts have been made to reduce these flexing and routing problems, the systems previously devised have been difficult to adjust, expensive, and bulky. These prior attempts to improve the responsiveness and reduce flexing in brake cable systems have therefore not gained widespread commercial acceptance.
In a conventional rotatable brake coupling system for exerting tension on a brake mechanism at a plurality of force transmission locations, there are a number of functional problems. In all conventional systems a splitter is employed in the brake line at some intermediate location between the brake actuating mechanism on the bicycle handlebar and the separate locations at which force is transmitted to the brakes. In a conventional splitter system the splitter housing from which the branches of the force application segments of the cable extend bend in different ways. This causes flopping, wobbling, and poor adjustability of the rotor unit at which the forces from the branches of the brake cable are applied.
When the splitter is free to move relative to the handlebars and steering tube of the bicycle, brake modulation is lost. That is, energy applied to operate the brake lever is lost in pulling the splitter lug, which in turn pulls the splitter in a lateral direction. Because the splitter is not fixed, fatigue to the cable is created over time by the expenditure of energy just to overcome the friction created by the splitter. This results from the awkward arcs of the two force transmission cable segments where they leave the rotatable brake coupling rotor and are routed toward the brake lever.
Also, the use of a conventional splitter at an intermediate location in the overall length of the cable makes it difficult to route and tie the cable to the bicycle frame bars without causing odd bends in the cable sheath. This has the effect of causing poor braking, poor brake modulation, and flopping.
Different manufacturers have attempted to reduce these problems in freestyle braking systems by offering different sizes of bicycle cables. However, the limited number of sizes offered does not effectively address the needs of the user. Furthermore, post-purchase customization of a bicycle cable in order to make it perform in a way for which it is not designed often negatively affects the braking power. Braking modulation is lose and cable life is shortened. Also, because there are so many cables housing, post-purchase length customization of the cable housing is time consuming and makes brake system adjustment difficult.
Conventional splitters also employ numerous parts. The various interconnections in the splitter housing produce excessive flexure and friction in the cable system. The two-from-one branching in the external design of conventional cable splitting systems forces the sheaths of the force transmission cable segments into unnatural positions in response to brake cable "pull back". The splitter lug must then compensate for the increase in load that is caused by exerting the force at angles that are created by the divergence of the force transmission cable segments from the rotatable brake coupling toward the splitter junction. This results in greater friction, less brake modulation, and eventual cable failure at the brake lever lug.
Conventional splitter designs also involve manufacturing problems. The conventional construction of a splitter involves a housing that has three different sections with six separate ends. Each end in the housing must connect to or interact with a different, specific element. The splitter housing requires the fabrication of two plastic pieces, each of which must be machined or cast, each of which needs paint, and one of which must be threaded. The proper fabrication of the splitter housing is therefore both difficult and expensive.
Also, cable assembly of a conventional splitter is very cumbersome and time consuming. In a conventional cable system for a rotatable brake cable coupling twenty-three separate parts must be assembled together.